It must be hard for Martin Amis, never quite knowing if he's a national treasure or a national embarrassment. His output in the first few years of this century, particularly the career lows of Yellow Dog (2003) and his books on Stalin and terrorism, saw him firmly established as the embarrassing uncle of English letters – well past his prime, creepy, grandiose, given to unhinged outbursts about "the age of horrorism" and "the worldflash of a coming future". But in recent years, things have unmistakably looked up: his last novel The Pregnant Widow (2010) was his best since the glory years of the 1980s; Amis the journalist seems to have wisely given up trying to pass himself off as a clash-of-civilisations man, in favour of writing excellent criticism again.

Unfortunately, the epigraph of his new novel Lionel Asbo – about a yob who wins the lottery – suggests a serious relapse:

Who let the dogs in?…This, we fear, is going to be the question.Who let the dogs in?

Who let the dogs in?Who?Who?

For our more high-minded readers: this is a riff on the soca anthem "Who Let the Dogs Out?", a carnival favourite regularly voted one of the most annoying songs of all time. The effect is comparable to the old Peter Sellers joke of reciting Beatles lyrics in a Laurence Olivier voice, except that the comedy is not intentional. It suggests that Lionel Asbo is going to be a clueless foray into popular culture and working-class life, conducted with Amis's trademark gaudy, repetitive insistence. And so it turns out. The novel effortlessly exerts the car-crash fascination that long-term Amis-watchers know too well: surely he's not going to do that? My god, he's gone and done it. But this isn't the same as saying that it's irredeemably awful. It is, in many ways, an eccentrically impressive performance.

It was surprising that, in the acknowledgments to The Pregnant Widow, Amis thanked Jane Austen for the "penetrating sanity" she had imparted to the English novel. And not just because people usually thank their spouse and agent, rather than major canonical figures (he also thanked Shakespeare and Ted Hughes). It was surprising because sanity has not been the prevailing mood of his big novels since, say, London Fields (1989). Where Ian McEwan, the yin to his yang, has gone from foetid psychosexuality and high-temperature visions to stately realism and breezy comedy, Amis has gone in the opposite direction.

The case against the novels that followed London Fields is now well established. Amis, it is often said, has mistaken the nature of his talent. He was a brilliant comic novelist, but he felt compelled to take on ever more high-flown subjects: the Holocaust, the gulag, the cosmos, the deepest recesses of the human psyche. As with Woody Allen, people tend to prefer his early, funny ones. (Julie Burchill: "If Martin Amis had stuck to writing about smoking, shagging and snooker he might have been the next Nick Hornby.") No one doubts his linguistic gifts, but they have often led up him up blind alleys: the heavily brilliant narrating voice can stifle everything else in the novels.

It sometimes seems that the genre does not exist for what Amis wants to write. He could have been a terrific novelist, poet, journalist and critic. Instead, he jams everything into the novels: editorialising, lyric poetry, even lectures on literary history. In his last one, as the narrator awaits a life-changing sexual initiation at the hands of a perfunctorily characterised Scottish lady with an extraordinary arse, he wonders what genre he's in – social realism? comedy of manners? romance? – before plumping in the end for "pornotheological farce". That's not a bad description of his later novels. Typically, a thin comedy plot collides with dark, fevered visions, along with some deeply emotional, transparently autobiographical material. The resulting mess is then held together with a basic suspense hook. We are kept waiting for hundreds of pages for a heavily flagged murder or sexual betrayal or – in the case of the new book – to find out who let the dogs in.

Lionel Asbo is another pornotheological farce. At one level, it's a reasonably straightforward satire. Subtitled "State of England", and published soon after Amis's departure for America, decrying the country's "moral decrepitude", it is a full-on indictment of a debased culture. Lionel Asbo is a "brutally generic" yob. He looks a bit like Wayne Rooney: "the slab-like body, the full lump of the face, the tight-shaved crown with its tawny stubble". A debt collector, he lives in a tower in the London Borough of Diston (a cross between Dalston and dystopia?), an urban hell-hole with the fertility rate of Malawi and the life expectancy of Djibouti. He wears a mesh vest, he has a pair of psychopathic pit-bulls, he beats people up for no reason, and he can't talk proper (as Amis endlessly reminds us, spelling out his mispronunciations: his own name comes out as "Loyonoo"). He's so proud of his behaviour that he has changed his surname to Asbo by deed poll. Then, like Michael Carroll, the so-called King of the Chavs who won the lottery in 2002, he wins untold millions, and behaves in a tremendously vulgar fashion, drinking champagne out of pint glasses, buying a ridiculous house in the country, and courting a Jordan-style glamour model.

So it's a familiar line of attack – against unearned wealth and celebrity, vulgarity, fake tits, feckless chavs, slipping educational and moral standards (and, by implication, footballers). But, this being a Martin Amis novel, everything has to be much weirder than that. He seems very remote from the world he describes. The details are persistently wrong in jarring ways: the lottery is played by post; ageing single mums are addicted to the Telegraph cryptic crossword. Lionel's girlfriend is called "Threnody", meaning a poem of mourning (for some reason the inverted commas are crucial). When she's not having plastic surgery or appearing in Hello!, she's a poet whose fondest ambition is to win the TS Eliot prize. "Glamour and myself are virtually synonymous" is the sort of thing she says, just as the Sun uses terms such as "doxy" and "delightfully assured". The heightened style, as ever, brings its own oddities. London is called "the great world city" throughout, and there's a reference to "the infant's opiate – the syrupy suspension of the purple paracetamol", known to inhabitants of planet earth as Calpol.

But then the novel is not realistic, even by satirical standards. Amis seems to be writing a romance, in the late Shakespearean sense. Lionel has a nephew, a half-Trinidadian orphan named Desmond Pepperdine. Though brought up by his uncle, he's the opposite of him: kind, gentle and intelligent, probably Amis's most virtuous character. We know that he has full authorial approval, not least because – not unlike Amis – he is an etymology pedant and a usage bore, with a near-religious reverence for the Concise Oxford Dictionary. He will father a child later in the book, and, as usual when writing about parenthood, Amis goes into sentimentally incontinent mode: "That throbbing glow reminded him of the most courageous sound he had ever heard: the (amplified) beating of his unborn daughter's heart."

Every detail about Desmond suggests that we should approve of him, except one: in the first paragraph we learn that he's having a passionate affair with his granny. As in many recent Amis books, there's a hum of unresolved sexual weirdness about the whole project.

The stranger Lionel Asbo gets, the less it seems like a convincing indictment of England today – and the more it seems that Amis should have a nice lie down in a darkened room. But there are plenty of consolations: the poetic fragments (the "white-van sky of London"); the passing scraps of the saner novels Amis might have written. And not just these. In general, Amis only gets really interested in one character per novel (usually the Amis surrogate). This time, it's Lionel. Like Keith Talent from London Fields, he creates his own comic reality, semi-detached from the one the rest of us live in. He wears a cashmere West Ham scarf; he's so opposed to grassing up felons that he beats up Desmond for watching Crimewatch; he feeds his devil dogs on Tabasco and Special Brew. He speaks like no one on earth: "you never give them they Tabasco", he often complains. Yet you come to believe him, to be slightly scared of him, even to sympathise with his predicament. Lionel Asbo isn't a book that you'd press into someone's hands, like Money or The Rachel Papers. It is basically incoherent. Yet there's something powerful and authentic about "its wrongness, its deafened bad dream feel".